Don't forget to remain always within view (4,2,5)

'view' is the definition.
(thesaurus)

'don't forget to remain always within' is the wordplay.
I cannot quite understand how this works, but
'remain' could be 'keep' (keeping is a kind of remaining) and 'keep' is found in the answer.
'within' could be 'in' and 'in' is found in the answer.
The remaining letters 'sight' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

Can you help me to learn more?